1. Field of the Invention
The present invention relates to the observation of events by video camera techniques, and more particularly to the forming of a composite video signal which comprises the images formed by a plurality of video cameras, the images being interlaced through multiplexing to provide a single video output signal.
2. Description of the Contemporary and Prior Art
There are many instances where it is desirable to closely observe experimental or production phenomena through the use of video imaging techniques. Unfortunately, if such phenomena take place in extremely short time frames, these short time frames may be substantially less than the time necessary for a video camera to form an image. For instance, a standard broadcast video camera does not form an image less than once in every thirty-three milliseconds. If the event to be observed is random and/or occurs in a few milliseconds, there is an excellent chance that such an event will be entirely missed by the video camera.
The particular circumstance which generated the desire for a television system which would provide images faster than the fastest image obtainable by a single video camera was in the testing of superflywheel energy storage apparatuses. These superflywheels have very high energy storage capabilities. The energy storage capabilities, however, are limited by self-destruction caused through imperfections in the material used to fabricate the flywheels and imperfections in assembly. Because much effort is made in determining how assembly can be improved and exactly which material imperfections cause catastrophic failure, it is logically apparent that it is important to observe such failure precisely. Because catastrophic failure is a virtually instantaneous occurrence, observing this extent with a video camera which can only image once every thirty-three milliseconds or so is rather inadequate.
Efforts by others to improve the ability of video systems to observe very short events have been primarily directed toward shortening the length of time it takes a video camera to form an image. Rather than redesigning the video camera, the present invention teaches a method of obtaining a plurality of serial images with virtually no time therebetween, such system being constructed by utilizing presently available video cameras and current technology.
This is accomplished by directing a plurality of video cameras at the same event to be observed, for instance a spinning flywheel, and, sequentially triggering the video cameras to each form an image so that a plurality of images closely spaced together are formed. These images are multiplexed together to provide a single video output which is a composite of the interlaced images of all of the video cameras trained on the event to be observed.
While multiplexing of video signals is well known in the art, multiplexing has not heretofore been utilized to interlace a plurality of outputs of video cameras to form a single interlaced signal output as hereinbefore described.
Typical of prior multiplexed systems is that taught in U.S. Pat. No. 3,492,419 issued to M. Bartonik on Jan. 27, 1970 which discloses the use of several cameras which provide images of the same object or different objects wherein means are provided for switching between the cameras so that the output of one of the cameras can be elected for viewing. Bartonik provides for the transmission of signals from each camera on separate wave frequencies, the composite signal later being received at a location which separates the multiple components of the signal and displays them separately on distinct portions of a television screen. Successive switching between cameras to form a single high speed composite image, as taught by the present invention, is not disclosed nor contemplated since the purpose of the Bartonik apparatus is to permit selection of one of a plurality of images rather than forming a new composite image.
Similarly, U.S. Pat. No. 3,504,133 issued to R. F. White on Mar. 31, 1970 teaches the combining of a plurality of transmitted television signals which can be selectively displayed at a receiver station. These signals are separated at the receiver and are viewed individually.
Many prior art teachings concern signal multiplexing rather than camera multiplexing. For instance, U.S. Pat. No. 3,757,225 issued to E. M. Ulicki on Sept. 4, 1973 shows the multiplexing of a plurality of continuous parallel signals which are sequentially sampled and placed onto a single line. At another location, the multiplex signal can be demultiplexed back into its component signals wherein desired discrete signals can be selectively retrieved. This signal multiplexing is significantly different than successively switching on cameras as taught by the present invention. A similar arrangement as to audio signals is taught by U.S. Pat. No. 3,941,930 issued to K. Mohri et al on Mar. 2, 1976.
U.S. Pat. No. 3,946,155 issued to J. K. Houston et al on Mar. 23, 1976 discloses an optical scanning system wherein a rotating drum has a plurality of radiation detection elements which sequentially pick up an optical signal, the signals from a plurality of detection elements being serially and successively entered onto a single line. Each entered signal, corresponding to a particular element, is then communicated to a cathode ray tube and is displayed as a single raster frame. Signals from successive elements on the drum thus provide successive raster frames. A controlled device is provided which corresponds to the scanning rate resulting from the rotation of the drum with the scanning rate of the cathode ray tube. Gating is provided such that the cathode ray tube frame is scanned each time a pulse denoting the commencement of a scan by a succeeding detection element, or mirror, occurs. That is, each time a new detection element passes before the optical source, a cathode ray tube frame is scanned. The use of this technique in conjunction with a plurality of television cameras to form a composite image is not shown or suggested and this invention is directed toward providing an optical display which is undistorted in shape rather than providing high speed observation of an event through rapid sequentially formed images.
Other teachings in the prior art, such as that in U.S. Pat. No. 3,743,768 issued to G. V. Copland on July 3, 1973, disclose the modification of video frames by interlacing scans within the frame to increase the amount of data carried by a raster at any given time. The present invention, to the contrary, is concerned with providing successive frames from successively out-of-phase cameras and does not deal with the varying of any particular frame generated by any one of the plurality of cameras.
In general, other multiplexing schemes which provide for signal multiplexing are shown in U.S. Pat. Nos. 3,705,263 issued to L. E. Rittenhouse on Dec. 5, 1972 and 3,825,674 issued to J. W. H. Justice on July 23, 1974.
As is apparent from reviewing prior technology, the present invention provides a unique approach to solving the problem of dead-time between the forming of images in a video camera system by the multiplexing of the outputs of a plurality of cameras together to form an interlaced composite video signal which enables high speed viewing of a dynamic event.